A conventional heat exchanger includes a heat exchange core portion for performing heat exchange between a fluid and air. The heat exchange core portion is configured by a plurality of flat tubes in which the fluid such as water or refrigerant flows, and fins bonded to flat surfaces of the flat tubes. The fins of the heat exchange core portion are provided with louvers formed by cutting and standing the fin surfaces. Because the louvers are formed in the fins, it can prevent a temperature boundary layer from being continuously developed, thereby improving heat exchanging performance.
If the louvers are formed in a contact portion of the fin contacting the flat surface of the flat tube, a contact error may be easily caused at the contact portion between the flat tube and the fin. Thus, the louvers are generally formed in the fin at positions separated from the contact portion contacting the flat tube by a predetermined distance. Accordingly, when air passes the fins at the positions without having the louvers, heat exchanging performance on the air side of the heat exchanger may be not sufficiently improved.
Non-Patent Document 1 proposes a heat exchanger, in which circular-arc protrusion portions are provided at two end portions of the respective flat tubes thereby reducing an air amount flowing to the side of the fins without having the louvers (Non-Patent Document 1: JOURNAL OF NIPPONDENSO TECHNICAL DISCLOSURE, No. 70-139, Published on Feb. 15, 1990).
However, in the Non-Patent Document 1, the protrusion portions are only provided at the two end portions of the respective flat tubes in an air flow direction. Therefore, air can flow to the flat surfaces of the flat tubes between the tube end protrusion portions. Thus, air flows to the fins at positions adjacent to the contact portion without having the louvers, and heat exchanging performance on the air side of the heat exchange cannot be effectively improved.